一种能长到六英尺高的新入侵物种风滚草正在接管加利福尼亚的部分地区——科学家警告说，随着气候变化使其生长条件更加有利，风滚草可能会进一步扩散。
Salsola ryanii2002年在加利福尼亚首次被发现。它是由另外两种入侵物种组成的混合体——Salsola tragus原产于俄罗斯和中国Salsola australis来自澳大利亚和南非。科学家说，后者是“世界上最严重的杂草之一”，目前在美国48个州发现。然而，这个新物种比它的父母要大得多，长得也快，大约有6英尺高。
风滚草是一种在夏末从根部脱落的植物。它被风吹来吹去——它传播种子的方式。在这样做的时候，杂草会引起巨大的问题。它们会导致交通事故和财产损失。入侵物种也给农业和本地生态系统带来问题。
2018年4月，加利福尼亚州的维多利亚市成为全球头条新闻埋在风滚草里。市政府官员贴出了一张受灾房屋的照片，称大风导致了房屋堆积。
在...之后S.ryanii首次被发现时，研究人员开始记录植物的分布范围..他们很快发现它传播得很快——在过去的二十年里，它的传播范围已经扩大到最初被发现时的几倍。风滚草现在在加利福尼亚和亚利桑那州被发现。
发表在杂志上的一项研究显示AoB工厂,查普曼大学的莎娜·威尔斯和加州大学河滨分校的诺曼·艾尔斯特兰德研究了如何和为什么S.ryanii在如此短的时间内变得如此成功。
埃尔斯兰在一份声明中说:“萨尔索拉瑞安尼是一种讨厌的物种，取代了美国其他讨厌的风滚草。”。“它比早期版本更健康，现在我们知道原因了。”
动物倾向于用一组来自母亲的染色体和另一组来自父亲的染色体来繁殖，与动物不同，植物可以用两组以上的染色体来繁殖后代。这些植物被称为多倍体。大多数情况下，这些后代无法自我繁殖——当一个物种是新物种时，它处于不利地位，因为它没有与它完全一样的东西可以繁殖。
然而，混血儿也有优势。人们认为多倍体可以产生更强壮、更健康的植物。如果它没有长得比父母强壮，它会很快灭绝。
S.ryanii，双亲都有双染色体。在他们的研究中，威尔斯和埃尔斯特兰发现它比任何一个都生长得更旺盛S.耳屏或者S.澳大利亚。他们使用了2012-2013年和2014-2015年的两个花园研究，选择了两个所有三个物种生长的地点。植物是由种子长成并分布的。
在这个季节结束时，他们观察了数百种植物的质量和种子数量。调查结果显示S.ryanii比它的父母成功得多:“我们记录了新形成的异源多倍体的地上植株质量和地上体积与其祖先相比有所增加，”他们写道。的平均质量S.ryanii重5.8公斤，而它的父母平均重3公斤。
最后，研究人员表示，这种新的风滚草物种在未来几年可能会进一步扩大其范围:“这种适应性比较结合了以前的记录工作S.ryanii 's正在进行的快速范围扩展表明S.ryanii有可能成为有问题的入侵物种。"
他们还说，由于气候变化，该物种可能传播得更快、更远。S.ryanii生长晚于其他物种，因此可以从一些气候模型预测的加州降雨量增加中受益。威尔斯在声明中说:“如果气候变化使夏季降雨更加普遍，他们可能会很好地利用夏季降雨。”
和...说话新闻周刊她补充说:“很难知道气候变化将如何影响这些物种的未来分布，但是随着温度和降雨模式的变化，气候变化肯定会影响许多物种的分布范围。”
这篇文章已经更新，包括莎娜威尔斯的名言和更多关于风滚草重量的信息。
突击队在2014年清除新墨西哥州克洛维斯的杂草。科学家发现，一种新的杂交风滚草物种似乎将在亚利桑那州和加利福尼亚州接管。
MONSTER HYBRID TUMBLEWEED SPECIES IS TAKING OVER CALIFORNIA, SCIENTISTS WARN
Ａnew invasive species of tumbleweed that can grow up to six feet in height is taking over parts of California—and scientists are warning it could spread even further as climate change makes its growing conditions more favorable.
Salsola ryanii was first identified in California in 2002. It is a hybrid made up of two other invasive species—Salsola tragus, which is native to Russia and China, and Salsola australis, from Australia and South Africa. The latter, scientists say, is "one of the world's worst weeds" and is currently found in 48 U.S. states. The new species, is however, far bigger and faster growing than its parents, reaching about six feet in height.
A tumbleweed is a plant that breaks away from its roots towards the end of summer. It is blown around by the wind—its means of seed dispersal. In doing this, tumbleweeds cause huge problems. They can lead to traffic accidents and damage property. Invasive species also cause problems for the agriculture industry and native ecosystems.
In April 2018, the city Victorville in California made headlines across the globe after being buried in tumbleweed. City officials posted a photo of an affected house, saying high winds had caused the pile up.
After S. ryanii was first found, researchers started to document the plant's range.. They soon discovered it was spreading fast—in the last two decades its range has expanded to be several times larger than when it was initially identified. The tumbleweed is now found in California and Arizona.
In a study published in the journal AoB Plants, Shana Welles, from Chapman University, and Norman C Ellstrand, from University of California Riverside, looked at how and why S. ryanii has become so successful in such a short space of time.
"Salsola ryanii is a nasty species replacing other nasty species of tumbleweed in the U.S.," Ellstran said in a statement. "It's healthier than earlier versions, and now we know why."
Unlike animals, which tend to reproduce with one set of chromosomes from a mother and another from a father, plants can produce offspring with more than two sets. These plants are known as polyploids. Most of the time these offspring are unable to reproduce themselves—when a species is new it is at a disadvantage as it has nothing exactly like it to reproduce with.
Being a hybrid also has advantages, however. It is thought that polyploidy can result in a stronger, healthier plant. If it did not grow stronger than its parents, it would quickly go extinct.
S. ryanii, has double chromosomes from both parents. In their research, Welles and Ellstrand found it grew far more vigorously than either S. tragus or S. australis. They used two garden studies from 2012-2013 and 2014-2015, with two sites selected where all three species grow. Plants were grown from seed and distributed.
At the end of the season, they looked at the mass and seed numbers for hundreds of plants. Findings showed that S. ryanii was far more successful than its parents: "We document an increase in above-ground plant mass and above-ground volume in the newly formed allopolyploid compared to its progenitors," they wrote. The average mass of S. ryanii was 5.8kg, while its parents weighed an average of 3kg.
Concluding, the researchers say the new tumbleweed species is likely to expand its range even further over the coming years: "This fitness comparison combined with previous work documenting S. ryanii's ongoing rapid range expansion demonstrates that S. ryanii has the potential to become a problematic invasive species."
They also say the species may spread faster and further as a result of climate change. S. ryanii grows later than other species, so could benefit from increased rainfall predicted in California under some climate models. "They may be well positioned to take advantage of summer rains if climate changes make those more prevalent," Welles said in the statement.
Speaking to Newsweek, she added: "It is hard to know how climate change will impact future distributions of these species, but certainty as temperature and rainfall patterns shift it will impact the ranges of many species."
This article has been updated to include quotes from Shana Wells and more information about the weight of the tumbleweeds.
Commandos clear tumbleweeds from Clovis, New Mexico, in 2014. A new hybrid tumbleweed species looks set to take over in Arizona and California, scientists have found.
